Question

2. An advertising firm has an old computer that can prepare a whole mailing in 6 hours. With

the help of a newer model the job is complete in 2 hours. How long would it take the newer
model to complete the job alone?

Answer 1

The new model can do the entire work alone in 3 hours.

Explanation:

Let us assume that the newer model of computer can complete the job alone in x hours.

Therefore, in one hour this new model can do
`(1)/(x)` part of the job.

Again the old model can do the entire job alone in 6 hours,

So, in 1 hour the old model can do
`(1)/(6)` part of the job.

Therefore, if they work together, then in 1 hour they will do
`((1)/(6) +(1)/(x) )= (x+6)/(6x)` part of the job.

So, the entire work they can do together in
`(6x)/(x+6)` hours.

So, given that
`(6x)/(x+6)=2`

⇒ 6x = 2x + 12

⇒ x = 3 hours,

Therefore, the new model can do the entire work alone in 3 hours. (Answer)